trigger source

例句：

1. 1. The trigger source for this event wasa sudden drop in oil prices.
   这个事件的触发源是石油价格的突然下跌。
2. 2. Theresearch team identified the trigger source as acombination of factors.
   研究团队确定了触发源为多种因素的组合。
3. 3. The scientist discovered the triggersource of the disease, which was agenetic mutation.
   科学家发现了这种疾病的触发源，这是一种基因突变。